Siemens SIPART DR20 Technical manual

Compact Controller

SIPART DR20

Project Planning Manual 02.05

Order No. 6ZB5600-0AAO2-0BA0

Project Planning Manual SIPART DR20

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SIPART DR20 Project Planning Manual

SIPART DR20

Project Planning Manual

This edition 1990 of the Project Planning Manual describes the SIPART DR20 compact

controller in the design with software version A09 (see page 91). This device can be used

to implement all functions which have already been described in earlier documents. A

number of function extensions have been made compared to earlier devices; these are

especially identified.

Notice

The controller SIPART DR20 is powered by electricity. Certain components within electrical

instruments are by necessity subject to very high voltages. Serious physical injury or damage to

property / equipment may ensue if the hints in this manual are ignored. Only suitable qualified

personnel should use this controller. The trouble-free and safe operation depends on proper

transport, professional storage, as well as careful operation and maintenance.

Subject to change

SIPART, TELEPERM, SIMATIC and COROS are registered trade marks

of the Siemens Aktiengesellschaft

Project Planning Manual SIPART DR20

Contents Page

1. Fundamental Control Technology Terms 5

1.1 Control Loop 5

1.2 Sensors and Transmitters 5

1.3 Final Control Elements and Actuators 5

1.4 Controllers 6

2. The SIPART DR20 Controller 10

2.1 Application 10

2.2 Operation and Display Functions 11

3. Technical Description 13

3.1 Hardware 13

3.1.1 Front Module 14

3.1.2 Basic Circuit Board 15

3.1.3 Additional Modules (Options) 16

3.2 Software 18

3.2.1 Input Signal Processing 22

3.2.2 Input Signal Processing and Switchover 25

3.2.3 Control Algorithm 43

3.2.4 Output Signal Processing and Switchover 46

3.2.5 Restart Conditions 58

3.2.6 Optical Signalling of Functions and Operating State 58

3.2.7 Bus Interface 60

4. Technical Data 62

5. Mounting 70

5.1 Mechanical Installation 70

5.2 Electric Connection 70

5.2.1 Wiring 71

5.2.2 Serial Interface and Bus Driver 71

6. Adjustments and Operation 87

6.1 Process Operation 87

6.2 Parameterization 88

6.3 Configuring 89

6.4 Lamp Test 91

6.5 Display of Software Version 91

6.6 Further Information 91

6.7 Standard Measuring Ranges for Temperature 93

Measurements Using Thermocouples

7. Commissioning 95

7.1 Matching to Direction of Action 95

7.2 Matching of Step Controllers to Final Control Elements 96

7.3 Optimization Guidelines 97

8. Abbreviations 100

9. Ordering Data 101

10. SIPART Controllers in Systems 102

11. Representation of Various Setpoints 103

12. Planning Examples 108

SIPART DR20 Project Planning Manual

1. Fundamental Control Technology Terms

1.1 Control Loop

An automatic control system has the function of bringing the output variable x of a controlled

system to a predetermined value and to maintain this value against the influence of disturbances z.

With digital controller, the controlled variable x is measured cyclically and compared with the

command variable w. The resulting negative deviation xd = w - x is processed in the controller to

form the manipulated variable y which acts on the controlled system.

-xd

z2z3

wCommand variable

x Controlled variable

xd Negative deviation

y Manipulated variable

z Disturbance variables

1 Controlled system

2 Controlling means

Fig.1/1 Block diagram of a control loop

1.2 Sensors and Transmitters

The controlled variable may be any physical quantity. Frequently encountered variables in process

engineering are e.g. pressure, temperature, level and flow.

Certain sensors such as resistance thermometers, resistance transmitters and thermocouples can

be directly connected to the controller. Otherwise, transmitters supplying an electric output variable

must be connected between the sensor and the controller. Our controllers are designed for

transmitters with standardized signal outputs (0 to 10 V, 0 to 20 mA or 4 to 20 mA).

1.3 Final Control Elements and Actuators

In most cases in heating and process engineering, the manipulated variable y acts through a valve,

a damper or another mechanical positioning device on the controlled system. Three types of

actuators are possible to actuate such final control elements:

• Electric actuators, consisting of electric motor and gear unit. They have an integral action

and are driven by three-position step controllers. There are also electric actuators with

integrated (series-connected) positioners which then have a proportional action and are

driven by continuous controllers.

• Pneumatic actuators with compressed air as the supply and with electropneumatic positioner

or converter. These have a proportional action and are driven by continuous controllers.

Project Planning Manual SIPART DR20

• Hydraulic actuators with electrically driven oil pump and electrohydraulic positioner. These

have a proportional action and are also driven by continuous controllers.

Electric actuators with single-phase or three-phase motors are robust, economical and require

practically no maintenance.

Pneumatic actuators are faster than electric actuators and are also explosion-proof. However, they

are not particularly suitable for large positioning forces.

Hydraulic actuators are fast and can also be used for large positioning forces, but they are more

expensive than electric or pneumatic actuators.

step function

control action step response

Kp ∗xd

Kp ∗Vv ∗xd

y0=0

Kp ∗xd

PID

Kp ∗xd

1.4 Controllers

In the input circuit, the

controlled variable x is

compared with the

command variable W and

the negative deviation xd

is determined. This is

processed with or without

a time response into the

output signal. The output

signal of the amplifier can

represent the manipulated

variable w directly, e.g. if it

controls final control ele-

ments or actuators with a

proportional action. With

electric actuators, the

mani- pulated variable y

only appears after the

actuator. The positioning

increments required are

obtained as a PDM signal

from the con- troller output

by conversion.

Depending on the con-

struction of this circuit, the

controller has a

proportional (P),

proportional-differential

action (PD), proportional-

integral action (PI) or

proportional-integraI-diffe-

rential action (PID).

Fig. 1/2

Step responses with different control actions

SIPART DR20 Project Planning Manual

If a step function is applied to the controller input, then step responses corresponding to Fig. 1/2

are produced.

Characteristic values of the P controller are the proportional gain Kp and the working point yo. The

working point is defined as the value of the output signal at which the negative deviation becomes

zero.

In contrast to the P controller, a permanent deviation is avoided in the PI controller, irrespective of

the working point, the setting of the command variable and the variation in the disturbance

variables, by means of an integrating component. The characteristic value of the integrating

component is the reset time Tn.

The PID controller achieves an improvement of the dynamic control performance by the addition of

a D component. The D component is determined by the derivative action gain Vv and the

derivative action time Tv.

The controller output signals must be matched to the actuators. Two types of controllers are

common for the most important kinds of actuator:

Æthree-position step controllers for electric actuators and

Æcontinuous controllers for pneumatic and hydraulic actuators

The three-position step controller switches the electric motor of the actuator to clockwise rotation,

stop or counterclockwise rotation by means of relays or semiconductor switches and can affect the

positioning speed of the final control element by means of different on/off ratios.

+xd

w Command

variable

x Controlled

variable

xd Negative

deviation

y Manipulated

variable

1 Transmitter

2 Setpoint adjuster

3 Three-point

switch

4 Feedback with

time response

5 Control amplifier

6 Final control

element

Fig 1/3 Three-position step controller, functional diagram

The switching performance of the three-point amplifier is reproduced in Fig 1/4 as a pulse diagram.

Project Planning Manual SIPART DR20

∆y

Kp ∗xd

Kp Proportional gain

Tn Reset time

xd Negative deviation

∆y Manipulated variable

(controller)

y Manipulated variable

(motor)

Fig. 1/4 Three-position step controller,

transient function and parameters

The transient function produced at the final control element by these pulses resembles that of a

continuous PI controller. Therefore the parameters Kp and Tn are also applied to the description of

the transient function of three-position step controllers. This is referred to as quasi-continuous

control (see Fig. 1/4).

The response threshold A is adjustable in our controllers. Thus, for example, noise suppression

and a stabilizing effect can be achieved.

The main field of application of continuous controllers is in installations with pneumatic

actuators. The controller output signal of 0 to 20 mA or 4 to 20 mA acts continuously on the final

control element through an electropneumatic signal converter.

+xd 4

0.2 ... 1.0 bar

0 ... 20 mA

(4 ... 20 mA)

w Command variable

x Controlled variable

xd Negative deviation

1 Transmitter

2 Setpoint adjuster

3 Control amplifier

4 Electropneumatic

signal converter

5 Pneumatic final

control element

Fig. 1/5 Continuous controller,

functional diagram

Two-position or three-position controllers are used to activate relays, contactors or thyristor

switches for switching electric heaters or coolers. The two-position controller (Fig. 1/6) switches, if

the controlled variable goes below the value x1 or above x2. A continuous oscillation occurs whose

frequency depends on the delay time of the controlled system and the switching hysteresis of the

controller.

SIPART DR20 Project Planning Manual

Since the control result thus obtained does not completely meet the requirements in most cases,

the switching frequency is increased and the amplitude of the oscillation is thus reduced. The

performance of a P or PI controller can thus be achieved in many cases using a two-position

controller. In the SIPART DR20 the control amplifier is followed by a duty factor converter with

adjustable period, resulting in a PID two- position controller (Fig. 1/7).

1. Controller

2. Controlled system

OFF

Fig. 1/6 Two-position controller without feedback

+xd 34

1. Setpoint adjuster

2. Control amplifier

3. Duty factor converter

4. Controlled system

5. Transmitter

Fig. 1/7 SIPART DR20 two-position controller

In the case of controllers with mechanical contacts, the switching frequency possibly is limited

because of the contact life. However, if thyristor units are used as switching elements, the

switching frequency can be increased.

The control problem often requires the controller action to be divided between various final control

elements or manipulated variables, e.g. for heating and cooling. Two- position controllers are used

for these problems where the manipulated variables are divided into two sections and assigned to

two outputs. An adjustable dead zone is present between the two sections. A duty factor of 0 to

100 % is possibly in each section.

These controllers are also referred to as three-position controllers.

Project Planning Manual SIPART DR20

2. The SIPART DR20 Controller

2.1 Application

The SIPART DR20 is a stand-alone process controller for a wide range of applications in process

engineering, mechanical engineering and apparatus engineering. It is available in the following

designs:

• K controller with continuous output

for connection of pneumatic or hydraulic actuators with proportional action

• S controller with step output,

programmable either as:

- three-position step controller for electric actuators

- two-position controller with two outputs for heating and cooling

Its flexibility means that SIPART DR20 is suitable for designing simple control loops as well as for

solving control tasks in meshed controls. It can be used in conventional parallel wiring via its

analog and digital interfaces. In addition, it can be connected to higher-level systems (process

computers or control systems) via an addressable serial interface which can be retrofitted at any

time or incorporated into a central operating and monitoring system with a personal computer and

the SIPART software, if applicable also together with devices from the TELEPERM D range.

The SIPART DR20 can be programmed to the most common types of controller:

• Fixed setpoint controller with and without disturbance variable feedforward at

input and output

• DDC backup fixed setpoint controller

• Follow-up controller with and without local/remote switchover (SPC)

• Synchronization controller for controlled variable

• Ratio controller

In addition, the device can also be used as a ratio station, manual/automatic control station (also

DDC manual control station) and process indicator.

The control and display unit (front module) of the SIPART DR20 is sealed by a plastic foil so that

degree of protection IP 64 is possible with a suitable installation configuration. The mounting depth

of the device is very small so that it is not only suitable for panel and switchboard mounting but

also for direct installation in machines and equipment.

An extremely high reliability for the device has been achieved by extensive and expensive

measures during development and manufacture. In addition to appropriate selection of the

components used, a worst-case design of the circuits and a 24-hour burn-in with subsequent

computer-controlled final test, special measures have been included to provide an interference-free

design of the circuits and high noise immunity towards RF sources.

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